Heat control system and switching mechanism therefor



y 1937. I c. HOTCHKISS 2,080,718

HEAT CONTROL SYSTEM AND SWITCHING MECHANISM THEREFOR Filed May 13, 19333 Sheets-Sheet l 2 v 3a 48 l 5 2% 39 16 5| fl 3a 4o 1 H 0 5 49 k 52A 47v CLIFFORD HOTCHKI SS y 1937. c. HOTCHKIS'S 2,080,718

HEAT CONTROL SYSTEM AND SWITCHING MECHANISM THEREFOR Filed May 15, 19333 Sheets-Sheet 2 'II 4 p "0111111111111 CLIFFORD HOTCHKISS May 18, 1937.c. HOTCHKISS HEAT CONTROL SYSTEM AND SWITCHING MECHANISM THEREFOR FiledMay 15, 1955 s Sheets-Sheet 3 CLIFFORD HOTCHKI 55 Patented May 18, 1937UNITED STATES PATENT' OFFICE HEAT CONTROL SYSTEM AND SWITCHING MECHANISMTHEREFOR Clifford Hotchkiss, Milwaukee, Wis., assignor toMinneapolis-Honeywell Regulator Company, Minneapolis, Minn., acorporation of Delaware Application May 13, 1933, Serial N0. 670,861

1'! Claims.

, and, in fact, for the control of combustion in any manner whatsoever.The switching mechanism of the present invention is particularly adaptedfor use in the various aforementioned control systems but this switchingmechanism also has general utility in the field of automatic controls.

One of the objects of the present invention is the provision of aswitching mechanism comprising a plurality of switches operated by asingle actuator, together with means whereby all of the switches may beadjusted in unison and additional adjusting means whereby one of theswitches may be additionally adjusted in respect to the other of theswitches.

A further object of the invention is the improvement upon thoseswitching mechanisms sometimes referred to as three-position switcheswherein a switch assumes a first circuit controlling position, is movedto a second circuit controlling position and then returns to its firstcircuit controlling position upon movement of an actuator in a singledirection. It is an object of the present invention to provide means formanually latching such a three-position switch in its second circuitcontrolling position when the actuator is in such position that theswitch would normally assume its first circuit controlling position,together with means whereby the switch will be released for automaticcontrol upon movement of the actuator to such a position that the switchwould normally be moved to its second circuit controlling position.

A further object of the invention is the provision of a three-positionswitching mechanism,

together with a second switching mechanism which is moved from one ofits circuit controlling positions to its other circuit controllingposition while the three-position switching mechanism is maintained inits second circuit controlling position. More specifically, the secondswitching mechanism is provided with means whereby it may be operatedwith or without an adjustable differential.

A further object of the invention is the pro-- vision of a combustioncontrolling system in which the device which controls combustion isoperated to decrease combustion when a temperature or pressure conditionproduced by combustion either rises above a predetermined maximum orfalls below a predetermined minimum.

In addition, it is an object of this invention to provide means forintermittently increasing combustion sufiiciently often to maintain e.fire when the system is operating under low heat requirement conditions.

Specifically, it is an object of this invention to provide a system forthe control of a solid fuel stoker mechanism, whereby the stoker will bestopped when the temperature of combustion becomes too high, will alsobe stopped when the temperature of combustion falls to a pointindicating that the fire has gone out and wherein the stoker will beoperated sufliciently often to normally maintain the fire alive when thesystem is operating under low heat requirement conditions. The inventionalso contemplates a system of the aforementioned type which includes athermostat responsive to the temperature of the space to be heated andoperative to start and stop the stoker in response to changes of suchspace temperatures.

Further objects of the invention will become apparent as the descriptionthereof proceeds and for a more complete understanding of the invention,reference should be had to the following description and accompanyingdrawings in which:

Fig. 1 is a front switching mechanism embodying vention;

Fig. 2 is a sectional 2-2 of Fig. 1;

Fig. 3 is a schematic wiring diagram showing the heat control systemwhich is the subject matter of the present invention;

Fig. 4 is a perspective view of a modified form of the switchingmechanism shown in Figs. 1 and 2; and,

Fig. 5 is a detail of a part of the mechanism of Fig. 4.

Referring first to Figs. 1 and 2 of the drawings, a base indicated at "Jsupports a sub-base II- by means of suitable connecting mechanism l2,which herein take the form of screws; nuts, and spacing sleeves. Thesub-base H' is provided with a circular opening I3 which receives acircular plate l4. A tubular member I5 is secured to one side of plateI4 and an adjusting handle 16 is secured to the other side thereof. Acylindrical member l1 surrounds tubular member l5 and one end of thiscylindrical member I1 is slightly expanded as indicated at IS. Theexpanded end l8 of cylinview'of one form of the the present inview takenabout on line drical member I! covers the slight space between circularplate l4 and the periphery of the opening 13, abutting both the sub-baseII and the circular plate I4 in such a manner that circular plate l4 maybe rotated by adjusting handle l6 but is prevented from moving out ofalignment with sub-base H in one direction. A collar 19 engages theexpanded end l8 of cylindrical member H to hold the same in its properposition. A bracket 20, which is secured to sub-base ll, bears against abulged portion 2| of adjusting handle l6 and prevents axial movement ofcircular plate l4 in a direction away from the end l8 of cylindricalmember H. In this manner, circular plate l4 may be rotated by adjustinghandle l6 but cannot move out of alignment with the plate of sub-base ll in either direction. A suitable scale plate 22 is secured to sub-basel I by any usual means, extends above the top of base l0 and cooperateswith a pointer 23 formed in adjusting handle l6. The scale plate 22 maybe provided with suitable indicia as indicated at 23A.

One end of a helically coiled bi-metallic element 24 is secured to thefree end of tubular member l5, as indicated at 25, and the other endthereof is secured, as indicated at 26, to a torsion rod 21 whichextends through the bi-metallic coil 24, tubular member l5, circularplate l4 and associ ated parts, and terminates within the space tweenbase l0 and sub-base H. A collar 28 is secured to this end of torsionrod 21 by means of a set-screw 29 and extends through a suitable openingin base l6 and terminates in front of said base. Collar 28 carries a camplate 30 which will be hereinafter described in more detail.

A switch supporting bracket 3i has one of its ends secured to the frontof base Ill and its other end carries a pin 32, the axis of which is inalignment with the axis of torsion rod 21. A mercury switch clip 33 andan actuating arm 34 which are secured together are pivotally mountedupon pin 32. A leaf spring 35 has one of its ends secured to bracket 3|and presses against actuating arm 34, whereby the arm 34 and the mercuryswitch clip 33 are frictionally held against the enlarged head of thepin 32 in such a manner that the mercury switch clip 33 and theactuating arm 34 will be frictionally retained in any position to whichthey are moved. The cam 36 is provided with a struck-up portion 36 whichoperates as an actuating pin for the purpose of engaging actuating arm34 upon movement of cam plate 30 in one direction. An arm '31, which isloosely journaled upon collar 28, is provided with a bent-over portion38 which extends in front of cam plate 30 and receives a set-screw 39for adjustably securing the arm 31 in any desired position. The camplate 30 is preferably provided with suitable indicia 46, whichcooperates with the pointed end of bent-over portion 36. The set-screw39 acts as an actuating pin which engages the other side of actuatingarm 34 upon movement of the cam plate 36 in the reverse direction tothat resulting in engagement of arm 34 by pin 36. By loosening set-screw39, and moving arm 31 in accordance with the indicia 46 on the cam plate30, the amount of lost motion between actuating pins 36 and 39 may beadjusted as desired. A mercury switch 4| is carried by mercury switchclip 33.

The base It) supports a pin 42 upon which is pivoted a U shaped plate 43which in turn carries a second mercury switch 44 by means of a mercuryswitch clip 45A. The plate 43 likewise carries a horizontally adjustableplate 45 which is provided with a bent-over extension 46 that operatesas a cam follower and normally bears against and engages an irregularcam surface formed in the cam plate 30. The cam plate 36 has cut-outportion leaving two circumferential cam surfaces 41 and 48 which areequally spaced from the center of cam plate 36 and a thirdcircumferential cam surface 49 which is spaced a smaller distance fromthe center of cam plate 36. The cam surfaces 41 and 46 are joined to thecam surface 49 by means of cam surfaces 56 and 5| respectively. The camplate 30 likewise carries an adjustable cam 52 which can be adjusted sothat its cam surfaces coincide with the cam surfaces 49, 5! and 46 or sothat the cam surface 49 is in effect, prolonged and the cam surface 46,in effect, is shortened. The cam 52 is provided with a pointer 53 whichcooperates with suitable indicia 54 on the cam plate 30, whereby theproper adjustment of the cam 52 may be had, the cam 52 being secured inits adjusted position to cam 30 by any suitable means such as the screw52A.

A pair of brackets 55 carried by base 16 journal a manually operable pin56 which is biased to move downwardly by means of a light coiled spring51. The upper end of pin 56 is slotted and receives a pivoted catch 56,having a notch 59 which is adapted to engage the lower edge of plate 43.The catch 56 is also provided with a tongue 66 which engages the uppersurface of the upper bracket 55 when the notch 59 is engaged with plate43. In this manner, the plate 43 may be latched in such a position thatthe mercury in mercury switch 44 bridges the electrodes of the mercuryswitch when the position of the cam surface 41 is such that the mercuryswitch 44 would otherwise be in open circuit position.

For certain purposes, the switching mechanism may be used to control lowvoltage circuits and a transformer 6| may be carried by base I6 ifdesired. Likewise, it may be found desirable to mount a relay generallyindicated at 62 on base It).

Operation of the switching mechanism 0/ Figs. 1 and 2 In Figs. 1 and 2,the switching mechanism has been shown in its cold position with themercury switch 44 closed and in such position that the same would beopen it it were not for the fact that it is latched in closed positionby the latch 56 above described. Assuming that the temperature to whichbi-metallic thermostatic element 24 responds begins to rise, the cam 30will be rotated in counterclock-wise direction as viewed in Fig. 1.After the cam plate 36 has been thus rotated in a counterclock-wisedirection thorugh a relatively small arc, the cam surface 50 will engagecam follower 46 and begin to rotate plate 43 about pin 42 in acounterclock-wise direction.

Upon further rotation of cam plate 36 in the same direction, the camfollower 46 rides upon cam surface 49 with the result that plate 43 iselevated to such a position that the notch 59 of catch 56 is disengaged.Spring 51 thereupon moves pin 56 downward and the switching mechanism isthereupon subjected to automatic control. If the temperature should nowfall, the cam plate 30 will rotate in a clock-wise direction and camfollower 46 will ride down cam surface 56 and on to cam surface 41,thereby allowing plate 43 to move in a clock-wise direction about pin42, with the result that mercury switch 44 will move to open circuitposition. The plate 43 can thereupon be again manually latched in the 5position shown in the drawings by means of the latch 58.

Assuming however, that the temperature continues to rise, the set-screwor actuating pin 39. will engage arm 34 and rotate mercury switch 4| ina clock-wise direction until the same has been moved to opencircuitposition. If the temperature rises still further, the camfollower 46 will ride down the cam surface of cam 52 and again allowplate 43 to move to such a position that mercury switch 44 will beopened. Assuming that the temperature now falls, the cam follower 46will ride up the cam surface of cam 52, tilting plate 43 and reclosingmercury switch 44. If the temperature continues to fall, the actuatingpin 36 will engage the opposite side of actuating arm 34 and movemercury switch 4| to closed position. It will be noted that the mercuryswitch 4| is moved to closed circuit position by actuating pin 36 at alower temperature than that at which it was moved to open circuitposition by setscrew 39. This differential may be varied or entirelyeliminated by proper adjustment of the arm 31 and set-screw or actuatingpin 39. If the temperature continues to fall, cam follower 46 will ridedown cam surface 58 on to cam surface 41, whereupon mercury switch 44will be moved to open position where it will remain unless thetemperature again rises or unless the mercury switch 44 is relatched inclosed position as shown in the drawings.

Moving of adjusting handle l6 rotates circular plate l4 and tubularmember |5 with the result that the thermostatic element 24 is bodilyrotated. Such operation of adjusting handle |6 positions cam plate 38 ina new position for any given temperature to which thermostatic element24 responds. This adjustment will be referred to as a basic adjustmentsince it varies the temperature at which both mercury switches 4| and 44will be operated. In addition, the position of cam follower 46 may bevaried, whereby the on and off movements of mercury switch 44 at boththe high and low temperatures may be changed within reasonable limits.Likewise, the cam 52 may be adjusted so as to prolong or shorten the camsurface 49 with the result that'the high temperature at which mercuryswitch 44 will be opened and closed may be additionally varied.

The switching mechanism of Figs. 1 and 2 therefore provides a firstswitch 44 which is in open position when the temperature is high, whichis in closed position when the temperature is intermediate and which isin open position when the temperature is low. The various temperaturesat which this switch 44 is operated may be adjusted and in eachinstance, the various adjustments are interposed upon other basicadjustments. Likewise, the switch 44 may be latched in closed positionwhen it would normally be open because of a low temperature at thethermostatic element 24, the arrangement being such that the mercuryswitch 44 returns to automatic control upon a risein temperaturesufficiently great to move the mercury switch 44 to closed position, ifit had not already been latched in such position.

The switching mechanism in Figs. 1 and 2 includes a second switch 4|which may be operated either with or without an adjustable differentialand is moved from open to closed position and back again by reason oftemperature fluctuations which are not great enough to move switch 44from its closed position. It will therefore be seen that the operationof switch 4| has a definite relationship to the operation of switch 44.

Turning now to Fig. 3 of the drawings an electrically operable deviceherein referred to as a stoker motor is'indicated at 65.. The coil 66 ofrelay 62 is adapted to move switch arms 61 and 68 into engagement withcontacts 69 and 10 when energized, the switch arms 61 and 68 beingbiased to open position. A main control switch in the form of abi-metallic room thermostat is indicated at 1| and includes contactblades 12 and 13 which are sequentially engageable with contacts 14 and15 upon temperature fall. Line voltage wires 16 and 11 supply electricenergy to stoker motor 65 and likewise to the primary 18 of a step-downtransformer 19, having a low voltage secondary 80. The system may alsoinclude a usual 'limit control to prevent an excessive temperature orpressure condition in the furnace or boiler, if desired. A limit control8| is herein shown as comprising a pair of contact blades 82 and 83which sequentially disengage contacts 84 and when the temperature orpressure of the boiler becomes too high. Contact blades 82 and areinsulated from each other. Such limit controls are well known in the artand a more specific description thereof is therefore deemed unnecessary.The specific connections between the various switches and devices shownin Fig. 3 will'b'e described under operation.

Operation of the system of Fig. 3

switches 44 and 4| indicates that their actuator is in its coldposition. The switch 4| is unable to actuate relay coil 66 and operatesstoker motor 65 because switch 44 is in the open circuit position.

If it now be desired to start up the fire and put the system intocondition for automatic operation. the combination high limit andout-fire 'switch 44 should be latched in closed circuit position in themanner previously described. in connection with Fig. 1 and Fig. 2. Suchclosure of the combination high limit and out-fire switch 44 establishes'an energizing circuit for relay coil 66 through hold-fire switch 4| asfollows: secondary 88, wire 86. wire 81. contact 85, contact blade 83,wire 88, wire 89, wire 90, holdfire switch 4|, wire 9|, wire 92. wire93, switch blade 82. contact 84, wire 94. w re 85, relay coil 66. wire96, combination high limit and out-fire switch 44 and wire 91 tosecondary 88. Energization of relay coil 66 attracts switch arms 61 and68 and moves them into engagement with contacts 69 and 10 respectively.

Engagement of switch arm 61 with contact '69 establishes a holdingcircuit for relay coil 66 independent of contact 84 and contact blade 82which holding circuit is as follows: secondary 80, wire 66, wire 81,contact 66, contact blade 96,

" wire 68, wire 69, wire 96, hold-fire switch 6|, wire 98, wire 99,switch arm 61, contact 69, wire I66, relay coil 66, wire 96, combinationhigh limit and out-fire switch 46, and wire 91 to secondary 8D.Engagement of switch arm 66 with contact 10 energizes stoker motor 66 asfollows: line I6, wire 1M, contact 16, switch arm 66, wire I62, stokermotor 66, and wire I63 to line I1.

The stoker motor is now operating and if the fire is rekindled,manually, the fire will begin to build up. The thermostatic element 26of switching mechanism of Figs. 1 and 2 preferably responds to thetemperature of combustion and is preferably placed in the stack of thefurnace or boiler. The increase in combustion temperature, due to there-establishment of combustion, first operates to release the latchingmechanism which returns the combination high limit and out-fire switch64 to automatic control. This increase in temperature, as previouslyexplained in connection with Figs. 1 and 2, is sufllcient thatcombination high limit and out-fire switch 46 is automaticallymaintained in closed circuit position.

As the stoker continues to operate, the temperature of combustion willrise suillciently to move hold-fire switch ll to open circuit position,whereupon relay coil 66 will be de-energized, allowing switch arms 61and 66 to move to the positions shown in Fig. 3, resulting in thede-energization oi stoker motor 66. The temperature of combustion willnow begin to fall and when it has lowered sufllciently, the holdfireswitch ll will again be moved to closed cir- 1 cult position, whereuponthe stoker will be again put into operation to feed fuel to the fire.Normally, the fire will still be in such condition that the new fuel fedthereto will become ignited and in this manner the fire-bed will be keptalive by the operation of hold-fire switch ll. If, for any reason, thefire should go out, the temperature of combustion will fall to such apoint that combination high limit and out-fire switch 66 will move toopen circuit position, whereupon the system will again be renderedinoperative until the fire is rekindled and combination high limit andout-fire switch 66 is again manually latched in closed circuit position.K

Assuming that the fire is properly maintained by the operation ofhold-fire switch II, the temperature of the space to be heated willfinally fall below the point desired, resulting in engagement of contactarm 12 with contact 16 a and then contact arm 13 with contact 16. If thearms 61 and 66 as hereinbeiore described, resulting in the establishmentof the aforementioned energizing circuit for stoker motor 66 and theestablishment of a holding circuit for relay coil 66 which isindependent of contacts 16 and 66 and contact blades 16 and 62. Thisholding circult is as iollows: Secondary 66, wire 66, wire 61, contact65, contact blade 66, wire 66, wire 66, wire I, contact H, contact blade12, wire I66, wire 99, switch arm 61, contact 69, wire I06, relay coil66, wire 66, combination high limit and out-fire switch 66 and wire 91to secondary 66.

It the stoker 66 were already in operation by reason of closure ofhold-fire switch 4|, then the last described holding circuit wouldbecome established upon engagement of contact blade 12 with contact 14with the result that stoker operation would be maintained upon openingof hold-fire switch 4| as long as contact blade 12 remained inengagement with contact 14.

If the temperature of combustion should become higher than desired asdetermined by the adjustment of the switching mechanism of Figs. 1 and2, combination high limit and out-fire switch 44 will be moved to opencircuit position, resulting in de-energization of relay coil 66 andstoker motor 66. If the stoker motor 66 is decnergized in this manner,the temperature of combustion will fall until combination high limit andout-fire switch 46 is automatically reclosed, whereupon relay coil 66will againbe energized and stoker motor 65 put into operation.

Likewise, if the room thermostat continues to call for heat and thetemperature of combustion does not become excessive, but the temperatureor pressure of the boiler becomes excessive, resulting in disengagementof'contact blade 62 from contact 64 and then contact blade 63 iromcontact 66, energization oi relay coil 66 will be interrupted, resultingin stopping of the stoker motor 66. When the boiler pressure ortemperature has thereafter lowered sufllciently to cause re-engagementof contact blades 63 and 62 with contacts 66 and 64 and ii the roomthermostat H is still calling for heat, the relay coil 66 will again beenergized in the manner above described to again place the stoker motor66 into operation. when the room temperature is restored so as toseparate" contact blade 13 from contact 16 and then separate contactblade 12 from contact 14, relaycoil 66 will be de-energized and thestoker motor 66 placed out of operation.

From the foregoing discussion oi. Fig. 3, it will be apparent that thesystem disclosed therein provides for operation of the stoker motor 66sufllciently often by the hold-fire switch ll to keep the fire aliveunder normal conditions 0! operation. In addition, the stoker motor ,66may be operated whenever the room temperature drops below the desiredpoint, since the room thermostat II and the hold-fire switch ll areconnected to the relay coil 66 in parallel. Furthermore, ii thetemperature of combustion becomes too high, the stoker motor 66 will bestopped by the combination high limit and out-fire switch 46 until suchtemperature falls to a safe amount. It should be noted that thecombination high limit and out-fire switch 44 serves a dual purpose forit will also stop the stoker motor 66 when the temperature of combustionfalls to a point as to indicate that the fire has become extingulshed'oris not likely to pick up if further fuel is fed to it. It should also benoted that the combination high limit and out-fire switch 46 and thehold-fire switch 4| are operated by a single thermostatic element. Itshould also be noted that if the fire should become extinguished, thesystem will be rendered inoperative until manual attention is given andthat provision is made whereby the stoker may be manually put intooperation with a subsequent return to automatic control.

Turning now to Figs. 4 and 5, a modified switching mechanism is shownwhich may be utilized in the system of Fig. 3 in place of the switchingmechanism shown in Figs. 1 and 2. A base gener-.- ally indicated at Hcomprises a flanged metallic member III and a panel H2 of insulatingmaterial, part of metallic member III being cut away in order to allowthe securing of certain electrical parts directly to the insulatingpanel H2. A subbase of heat insulating material is indicated at H3 andis held in spaced relation in respect to base H0 by any suitable meansnot shown'. A tubular member .I I4 has one of its ends expanded asindicated at H5 and this expanded end H5 is held in abutting relationwith the sub-base I I3 by means of a collar H6 which is secured tosubbase H3 by screws H1. The sub-base H3 is provided with a circularopening H0 in which a plate H9 is disposed. A tubular member I20 whichis concentric with and disposed within tubular member H4 has one of itsends secured to one side of plate H9. To the other side of plate H9 issecured an adjusting and indicating handle I2I which is provided with araised portion I22. The tubular member I20 and adjusting handle I2I aresuitably secured to plate II9 by means of rivets I23. The plate H9 isallowed to rotate but is prevented from moving axially in one directionby abutting with the expanded end H5 of tubular member H4 and in theother direction by a retainer I24 which abuts the raised portion I22 ofadjusting and indicating handle I2I. A bi-metallic thermostatic elementI has one of its ends secured to the free end of tubular member I20,asindicated at I26, and the other end of bi-r'netallic thermostaticelement I25 is secured to one end of a torsion rod I21 as indicated atI28. The torsion rod I21 extends axially through bimetallic thermostaticelement I25, tubular member I20, plate H9, up-raised portion I22 ofhandle I2I, retainer I24 and base H0.

Adjusting and indicating handle I2I cooperates with a scale plate I29having suitable indicia I30 thereon. Movement of adjusting andindicating handle I2I across scale plate I29 rotates tubular member I20and thereby bodily positions the thermostatic element I25 whereby thatend thereof which is secured to torsion rod I21 may be manually made toassume varying positions while the temperature to which thermostaticelement I25 responds, remains constant.

The torsion rod I21 terminates shortly in front of base I I0 andsecurely carries an actuating plate I3I. An adjustable cam plate I32 ispivoted on actuating plate I3I at a point which is in alignment with theaxis of rotation of actuating plate I3I and torsion rod I21. A bracketI33 is secured to insulating panel H2 and. pivotally carries a switchoperating member I34. An adjustable mercury switch clip I is pivoted toswitch operating member I34 and is adjustably secured in the desiredposition by a screw I36. The mercury switch clip I35 supports a mercuryswitch I31 which corresponds to the combination high limit and hold-fireswitch M of the mechanism of Figs. 1 and 2 as will hereinafter appear.The axes of rotation of mercury switch clip I35 and switch operatingmember I34 are in alignment with the axes of rotation of torsion rod I21and actuating plate I3I. Switch operating member I34 is provided with aslot I30 which permits bodily adjustment of a screw I39 having anextended end I40 which extends into an irregularly shaped opening I4Iformed in actuating plate I3I. An indicator I42 is clamped againstswitch operating member I34 by screw I39 and cooperates with indicia I43to indicate the adjusted position of the extended end I40 of screw I39.

The mechanism of Figs. 4 and 5 thus far described operates as follows:Upon a rise in the temperature to which bi-metallic element I25responds, the torsion rod I21 and actuating plate I3I are rotated in acounter clock-wise direction as viewed from the front in Fig.4 and aftera certain amount of lost motion is taken up, the right hand edge formedby the opening I in the actuating plate I3I engages the extended end I40of screw I39 and tilts switch operating member I34 and mercury switchI31 in counter clock-wise direction to open the circuit through mercuryswitch I31. Likewise, upon temperature fall, after the lost motion hasbeen taken up, the left hand edge formed by the opening MI in actuatingplate I3I will engage the extended end I40 of screw I39 and tilt switchoperating member I34 and mercury switch I31 in a clock-wise direction toclose the circuit through mercury switch I31. Bodily adjustment of screwI39 changes the location of extended end I40 thereof in respect to theopening I4I formed in actuating plate I3I, whereby to vary the amount oflost motion between actuating plate I3I and the extended end I40 ofscrew I39 from a maximum to a minimum with the result that thetemperature differential required to operate mercury switch I31 may beadjustably predetermined. The irregular configuration of the opening MIin actuating plate I3I is provided in order that equal bodily movementsof screw I39 in accordance with the indicia I43 will result in equalchanges in the operating differential for mercury switch I31. Operationof adjusting and indicating handle I2I bodily moves the thermostaticele'ment I25 and changes the basic setting at which mercury switch I31will be operated. The mercury switch I31 may also be manually adjustedto a certain extent by loosening screw I36 and rotating mercury switchclip I 35. This adjustment is quite important in relation to the otherfunctions of the switching mechanism of Figs. 4 and 5 as willhereinafter become apparent.

The lower periphery of actuating plate I3I and the lower periphery ofcam plate I32 cooperate to form a cam surface which is engaged by a camfollower I44 which is formed by bending over one end of a lever I46which is pivoted to a slidable mounting I41 as indicated at I49. Theother, or left hand end of lever I46 supports a mercury switch clip I49which carries a mercury switch I50. The mercury switch I50 correspondsto the combination high limit and out-fire switch 44 of the mechanism ofFigs. 1 and 2. With the parts in the position shown, the cam followerI44 is out of engagement with actuating plate I3I and cam plate I32 andis held in such position by a latch plate I5I which is formed with ahook I52. The circuit through mercury switch I 50 is closed. If thelever I46 is rotated slightly in clock-wise direction about its pivotI48, the cam follower I44 will disengage the hook I 52 and allow latchplate I5I to rotate about its pivot I53 in a counter clock-wisedirection. If lever I46 is now released, it will rotate in counterclock-wise direction about its pivot I48 by gravity, and the camfollower I44 will engage the periphery of actuating plate I3I whereuponthe lever I46 will assume such position that the circuit through mercuryswitch I50 is broken.

In order to relatch mercury switch I50 in closed circuit position, theslideable mounting I41 is moved to the right by grasping the operatinghandle I54 and the cam follower I44 will engage and ride under hook I52.Subsequent movement of slidable mounting I41 to the left will thereupon.cause the parts to assume the position shown in Figs. 4 and 5 whereinthe cam follower I44 is engaged with hook I52 and the mercury switch I50is latched in closed. circuit position. Excessive clock-wise rotation oflatch plate I5I is prevented by a lug I55 which is struck-up from themetallic member II I of base IIO.

If the temperature to which thermostaticelement I25 responds shouldrise, actuating plate I3I and cam plate I32 will be rotated in a counterclock-wise direction and the projected portion I56 of actuating plateI3I will engage cam follower I44 and slightly depress the right hand endof lever I46. Such depression of the right hand end of lever I46 willdisengage cam follower I44 from hook I52 and latch plate I5I will rotatein a counter clock-wise direction to its inoperative position. Uponfurther counter clock-wise movement of actuating plate I3I, extensionI40 of screw I39 will be engaged as hereinbefore described with theresult that mercury switch I31 will be moved to open circuit position.Further counter clock-wise rotation of actuating plate I3I will allowcam follower I44 to ride down the edge I51 of cam plate I32 until thelever I46 rotates sufiiciently in a counter clock-wise direction to.open the circuit through mercury switch I50. This is the high limitcut-off position of mercury switch I 50. If the temperature to whichthermostatic element I25 responds should now decrease as previouslyexplained in connection with the system of Fig. 3, the cam plate I32 andactuating plate I3I will be moved in a clock-wise direction. Such motionwill depress cam follower I44 to again move mercury switch I50 to closedcircuit position. Continued movement of actuating plate I3I in aclock-wise direction in response to a further temperature fall willcause the extended end I40 of screw I39 to be engaged with the resultthat mercury switch I31 is moved to closed position as previouslyexplained. Further continued rotation of actuating plate I 3| and camplate I32 in a clock-wise direction will allow the cam follower I44 toride oil the projected portion I56 of actuating plate I3I, whereuponmercury switch I50 will move to open circuit position. This is thelock-out position corresponding to the lock-out position of switch 44 ofthe mechanism of Figs. 1 and 2 as explained in connection with thesystem of Fig. 3. As previously explained, mercury switch I50 willremain in this open circuit position until latched in closed circuitposition by proper manipulation of the slidable mounting I41.

The cam plate I32 is provided with a pointer I58 which cooperates withindicia I53 which is provided on actuating plate I3I. A screw I60permits of adjustment of cam plate I32 and such adjustment of cam plateI32 acts to extend or contract the cam surface formed in actuatingplate'I3I, which cam surface controls the operation of mercury switchI50 by means of cam follower I44.

The operation of the switching mechanism of Figs. 4 and 5 is identicalwith that of Figs. 1 and 2. The adjusting and indicating handle I2Iprovides for a basic adjustment, whereby both mercury switches I31 andI50 may be adjusted in unison. Bodily movement of screw I39 provides fora variable differential in the operation of mercury switch I31.Adjustment of mercury switch clip I35 provides an additional adjustmentfor mercury switch I31 which adjustment may be superimposed upon thebasic adjustment. Adjustment of cam plate I32 likewise provides anotheradjustment for mercury switch I50 which is superimposed upon the basicadjustment. The mercury switch I50 is a three-position switch which isoperated from open to closed and then again to open circuit positionupon temperature fall and may be manually latched in closed circuitposition when the temperature is so low that it would otherwise be inopen circuit position. The mercury switch I31 is moved to closed andopen circuit positions and vice versa while the mercury switch I50 ismaintained in closed circuit position during normal temperaturevariations. In actual construction, a relay, generally indicated at I6I, may be mounted upon insulating panel II2 of base IIO. Also, it may bedesirable to place a protecting tube I62 about thermostatic element I25.In addition, it may be desirable to mount a transformer on insulatingpanel II2.

From the foregoing description it will therefore be seen that thisinvention provides two modifications of a novel switching mechanism,having the many features pointed out in the introduction and throughoutthe specification. The invention also provides a novel system of'control wherein a burner apparatus is automatically operated sumcientlyoften to maintain the fire, may be operated as required by changes inthe temperature of the space to be heated, is temporarily shut down ifthe temperature of the combustion gases or the temperature of the boileror furnace become excessive and is permanently shut down if thetemperature of combustion falls to a point indicating that the fire hasbecome extinguished. The system is also so arranged that the burnerapparatus may be manually operated when the fire has become extinguishedand will return to automatic control as soon as the temperature ofcombustion rises to a point indicating that the fire again is capable ofautomatic control.

While specific embodiments of the switching mechanism have been hereindescribed and a single embodiment of the system has been disclosed, itis to be understood that many changes and modifications thereof could bemade without departing from my invention and I intend to be limited onlyby the scope of the appended claims.

I claim:

1. A device of the class described, comprising, in combination, anactuator, a member controlled thereby, means associated with theactuator for causing said controlled member to assume a first position,then a second position, and thereafter again assume the first positionupon movement of the actuator in a single direction, means for basicallyadjusting said first named means whereby the positions of the actuatorat which said first and second positions are assumed by the controlmember may be changed in unison, and means associated with said firstand second named means whereby the position of the actuator at whichsaid controlled member will assume one of said positions may be variedin respect to another of said positions.

2. A device of the class described. comprising. in combination, anactuator responsive to a physical condition, a switch controlled\thereby, means associated with said switch and actuator whereby theformer assumes open circuit position, then closed circuit position andthereafter open circuit position upon movement of the actuator in asingle direction, and means (or manually latching said switch in closedcircuit position when said actuator is in one of its positions resultingin movement of the switch to open circuit position, said means beingoperable upon return of said actuator to a position normally causingsaid switch to assume closed circuit position, to return said switch tothe automatic control of said actuator.

3. A switching mechanism of the class described, comprising, incombination, a first switch, a second switch, an actuator, and meansassociated with said actuator and" first and secand switches for causingsaid first switch to assume a first circuit controlling position whenthe actuator is in one position, to cause said first switch to assume asecond circuit controlling position upon movement of the actuator in onedirection, to cause said second switch to assume a new circuitcontrolling position upon further movement of the actuator in the samedirection and to cause the first switch to assume its first circuitcontrolling position upon still further movement of the actuator in thesame direction.

4. In combination, a thermostatic element, a switch, means associatedwith said thermostatic element and switch for operating the latter uponvariations in the temperature to which the tor mer responds, said meansbeing operative to cause said switch to assume a first circuitcontrolling position when the temperature at the thermostatic element isrelatively high, assume a second circuit controlling position upon afirst lowering in said temperature and reassume its first circuitcontrolling position upon still further lowering in said temperature,and means for manually latching said switch in its second circuitcontrolling position when said temperature becomes so low as to causesaid switch to move to its first circuit controlling position, said lastnamed means being operative to release said switch for automaticoperation by said thermostatic element upon a raising in the temperatureto which it responds.

5. In combination, a thermostatic element, a switch, means associatedwith said thermostatic element and switch for operating the latter uponvariations in the temperature to which the former responds, said meansbeing operative to cause said switch to assume a first circuitcontrolling position when the temperature at the thermostatic element isrelatively high, assume a second circuit controlling position upon afirst lowering in said temperature and reassume its first circuitcontrolling position upon still further lowering in said temperature,and means for manually latching said switch in its second circuitcontrolling position when said temperature becomes so low as to causesaid switch to move to its first circuit controlling position, said lastnamed means being operative to release said switch for automaticoperation by said thermostaticelement upon a raising in the temperatureto which it responds, a second switch, and means associated with thesecond switch and thermostatic element for moving the second switch toopen and closed positions while the first switch is maintained in itssecond circuit controlling position.

6. In combination, an actuator responsive to changes in a physicalcondition, a switch, connections between said switch and actuatoroperative to move said switch from a first controlling position to asecond controlling position and to return the same to said firstcontrolling position upon progressive movement of said actuator in asingle direction, a second switch, and connections between said actuatorand second switch operative to move said second switch to first andsecond controlling positions upon reverse movements of said actuatorwhile said first switch is maintained in its second controlling positionby said actuator.

7. In combination, an actuator responsive to variations in a physicalcondition, a first switch, connections between said first switch andactuator by which the actuator moves the first switch to open and closedpositions upon relatively small reverse movements thereof, a secondswitch, and connections between said second switch and actuator by whichthe actuator maintains. said second switch closed while the actuatormoves reversely through said relatively small movement and opens saidsecond switch upon suificient further movement of said actuator ineither direction.

8. In combination, an actuator responsive to temperature changes, afirst switch, connections between said actuator and first switchoperative to close the first switch when the temperature to which saidactuator responds falls to a first value and to open the first switchwhen the temperature to which the actuator responds rises to a secondvalue, a second switch, and connections between the second switch andactuator by which the actuator maintains the second switch closed duringsuch temperature fluctuations and opens the same upon a tall or rise ofthe temperature to which said actuator responds below said first valueor above said second value.

9. In combination, an actuator responsive to temperature changes, afirst switch, connections between said actuator and first switchoperative to close the first switch when the temperature to which saidactuator responds falls to a first value and to open the first'switchwhen the temperature to which the actuator responds rises to a secondvalue, a second switch, connections between the second switch andactuator by which the actuator maintains the second switch closed duringsuch temperature fluctuations and opens the same upon a fall or rise ofthe temperature to which said actuator responds below said first valueor above said second value, and means including a manually operablelatch to latch said second switch in closed position when thetemperature to which said actuator responds falls below said first valuethereby causing opening of said second switch, said means operating torestore said second switch to automatic control upon a subsequentsuificient rise in temperature to normally cause said second switch toclose.

10. A device of the class described, comprising, in combination, atemperature responsive actuator, a switch controlled thereby, meansassociated with said actuator for moving said switch from open positionto closed position and then back to open position upon continuousmovement or said actuator in a single direction, means operable tobasically adjust the temperature at which all of said switch movementswill occur, and additional adjusting means operable to vary the range oftemperature change required to cause all of said switch movements.

11. A device or the class described, comprising, in combination, atemperature responsive actuator, a switch controlled thereby, meansassociated with said actuator for moving said switch from open positionto closed position and then back to open position upon continuousmovement of said actuator in a single direction, means operable to Calbasically adjust the temperature at which all of said switch movementswill occur and additional adjusting means operable to individuallyadjust the points at which said switch will be moved t open circuitposition.

12. A switching mechanism of the class described, comprising, incombination, an actuator, a first switch, connections between said firstswitch and actuator by which said actuator moves said first switch froma first circuit controlling position to a second circuit controllingposition and back to said first circuit controlling position uponmovement of said actuator in a single direction, a second switch,connections between said actuator and second switch by which theactuator moves said second switch to first and second circuitcontrolling positions upon reverse movements of the actuator whilemaintaining the first switch in its second circuit controlling position,basic adjustment means associated with said actuator and both saidswitches operative to simultaneously adjust the operation of both ofsaid switches, and additional adjusting means associated with one ofsaid switches operative to additionally adjust the same withoutdisturbing the adjustment of the other of said switches.

13. A switching mechanism of the class described, comprising, incombination, an actuator, a first switch, connections between said firstswitch and actuator by which said actuator moves said first switch froma first circuit controlling position to a second circuit controllingposition and back to said first circuit controlling position uponmovement of said actuator in a single direction, a second switch,connections between said actuator and second switch by which theactuator moves said second switch to first and second circuitcontrolling positions upon reverse movements of the actuator whilemaintaining the first switch in its second circuit controlling position,basic adjustment means associated with said actuator and both saidswitches operative to simultaneusly adjust the operation of both of saidswitches, and additional adjusting means comprising an adjustablelost-motion connection associated with one of said switches.

14. A switching mechanism of the class described, comprising, incombination, an actuator, a first switch, connections between said firstswitch and actuator by which said actuator moves said first switch froma first circuit controlling position to a second circuit controllingposition and back to said first circuit controlling position uponmovement of said actuator in a single direction-a second switch,connections between said actuator and second switch by which theactuator moves said second switch to first and second circuitcontrolling positions upon reverse movements oi the actuator whilemaintaining the first switch in its second circuit controlling position,basic adjustment means associated with said actuator and both saidswitches operupon movement or said actuator in a single direction, asecond switch, connections between said actuator and second switch bywhich the actuator moves said second switch to first and second circuitcontrolling positions upon reverse movements of the actuator whilemaintaining the first switch in its second circuit controlling position,basic adjustment means associated with said actuator and both saidswitches operative to simultaneously adjust the operation of both ofsaid switches, and additional adjusting means operative to change therange of movement required of said actuator to move said first switchthrough all of its switching movements.

16. A switching mechanism of the class described, comprlsing, incombination, an actuator, a first switch, connections between said firstswitch and actuator by which said actuator moves said first switch froma first circuit controlling position to a second circuit controllingposition and back to said first circuit controlling position uponmovement of said actuator in a single direction, a second switch,connections between said actuator and second switch by which theactuator moves said second switch to first and second circuitcontrolling positions upon reverse movements of the actuator whilemaintaining the first switch in its second circuit controlling position,basic adjustment means associated with said actuator and both saidswitches operative to simultaneously adjust the operation of both ofsaid switches, and additional adjusting means operative to change one ofthe positions of the actuator at which said first switch is moved to itsfirst circuit controlling position.

17. In combination, an actuator responsive to changes in a physicalcondition, a switch controlled thereby, means associated with saidactuator for moving said switch (run one controlling position to asecond controlling position and to return the same to said firstcontrolling position upon progressive movement of said actuator in asingle direction, means operable to basically adjust the value of thecondi-- tion at which all oi said switch movements will occur, andadditional adjustment means operable to independently vary the value 01!the condition at which said switch returns from said second position tosaid first position upon movement of said actuator in said singledirection.

CLIFFORD HO'ICHKISS.

